Characterization of mutations in multi- and extensive drug resistance among strains of Mycobacterium tuberculosis clinical isolates in Republic of Korea

In order to characterize molecular mechanisms of first- and second-line drug resistance in Mycobacterium tuberculosis and to evaluate the use of molecular markers of resistance, we analyzed 62 multidrug-resistant, 100 extensively drug-resistant, and 30 pan-susceptible isolates from Korean tuberculosis patients. Twelve genome regions associated with drug resistance, including katG, ahpC, and inhA promoter for isoniazid (INH); embB for ethambutol (EMB), rpoB for rifampin (RIF), pncA for pyrazinamide (PZA), gyrA for fluoroquinolones; rpsL, gidB, and rrs for streptomycin; rrs and eis for kanamycin (KM); rrs and tylA for capreomycin (CAP); and rrs for amikacin (AMK) were amplified simultaneously by polymerase chain reaction, and the DNA sequences were determined. We found mutations in 140 of 160 INH-resistant isolates (87.5%), 159 of 162 RIF-resistant isolates (98.15%), 127 of 143 EMB-resistant isolates (88.8%), 108 of 123 ofloxacin-resistant isolates (87.8%), and 107 of 122 PZA-resistant isolates (87.7%); 43 of 51 STM-resistant isolates (84.3%), 15 of 17 KM-resistant isolates (88.2%), and 14 of 15 (AMK and CAP)-resistant isolates (93.3%) had mutations related to specific drug resistance. In addition, the sequence analyses of the study revealed many novel mutations involving these loci. This result suggests that mutations in the rpoB531, katGSer315Thr, and C-15T in the inhA promoter region, and gyrA94, embB306, pncA159, rpsL43, and A1401G in the rrs gene could serve as useful markers for rapid detection of resistance profile in the clinical isolates of M. tuberculosis in Korea, with potentials for the new therapeutic benefits in actual clinical practice.